Piston for internal-combustion engines.



G. K. DAVOL.

PISTON FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED OCT. 5. I911.

I Patented Oct. 12, 1915.

ATTOR/I/EIJ FIG. 2.

FIE. 5.

WITNESSES.

GEORGE K. DAVOL, OF SAN FRANCISCO, CALIFORNIA.

PISTON FORINTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent.

Patented ca. 12, 1915.

' Application filed October 5, 1911. Serial No. 652,921.

' taln new and useful Improvements in Pistons for Internal-Combustion Engines, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My, invention" has particular application to those internal combustion engines in which it is desirable for any purpose to present to the working gases within the cylinder, surfaces heated to a considerable temperature. This is sometimes desirable in order to insure the complete combustion of heavy oils, or tarry constituents of gas, or other fuels, with the proper combustion of which cold surfaces would interfere.

The end of the piston in all internal combustion engines is presented to the working gases or burning charge, and it is usually kept cool either by direct water cooling or by the conduction of its heat to the sides of the piston. In cases where it has been desirable, however, it has frequently been proposed to attach to the end of the piston, a shield, plate or cap, between which and the piston proper would be interposed a layer or thickness of some insulating substance, or

some substance which was a poor conductorof heat, and such arrangements have been tried. It has been fopnd, however, in trying such devices, that it is exceedingly difficult to secure such a cap or shield to the end of the piston, so that it would at all times tightly clamp and hold the thickness of non-conducting material in place owing to the effect of the heat in expanding the bolts or other means of attachment which secures the shield to the piston. It has been found that'if the slightest looseness be allowed to the non-conducting or insulating layers,

that is, if it is not at all times tightly com-- pressed against the end of the piston, it will very quickly abrade, disintegrate and wear away through the reciprocating movement of the piston together with the effect of the high temperatures and the movements of the gases. To overcome this difficulty and to provide an efficient means of securing such a cap or shield to the end of the piston, I employ a metal spring, arranged to exert a constant pull holding the cap or shield against the end of the piston; the spring being so designed that it will give to, or take up any expansion of the various parts or connections affected by the heat without having the force of its pull appreciably affected.

Between the cap or shield and the piston proper, I interpose a layer of asbestos, magnesia, or other suitable poor conductor of heat, which will stand the high temperatures, and this layer of material is always kept by the action of the spring tightly pressed against the end of thepis'ton.

In the accompanying drawings,-Figure I shows a section taken through'the center axis of a piston'connected to a piston rod. Fig. 2 shows a section taken through the center axis of a trunk piston designed to pitman or connecting rod. Fig. 3 shows a section taken through the center axis-of a trunk piston designed to be directly connected to a cross-head.

In all the figures the same numerals refer to the same parts.

Referring to Fig. 1, the piston proper 1, which is connected to the piston rod 2, has a shield or cap 3 which is made to fit on a shoulder 4-formed on the end of thepiston. Between this cap 3 and the piston is interposed a layer or layers of sheet asbestos or other suitable insulating material 5. The cap 3 is drawn against the end of the piston by two or more rods 6 which are screwed into the cap and pass through the end of the piston. Each of theserods 6 passes through hold a wrist pin for directconnection to a a helical spring 7 and has secured to its end a washer 8 against which the spring 7 bears. Each of the springs bears at its other end against a circular plate 9 through which the piston rod passes and which rests on a shoulder formed on the piston rod. It will now be understood that the springs, bearing at one end against the plate 9 exert a pres-' sure against the washers 8 on the ends of By this ar- In Fig. 2, I show a trunk piston with a y I modified arrangement of parts. In this case the insulating material 5 is placed inside of the shoulder i and is thus more protected from the direct action of the gases. In this form I use one central rod "6 to draw the cap 3 against the piston 1, and one spring 7. All these parts are placed behind the wrist pin 10 and connecting rod 11; As the action of the various parts is the same as explained in describing Fig. 1, this view re- I I of reciprocatlon in said cylinder, a proquires no further explanation.

In Fig. 3 show a trunk piston designed to be connected directly to a cross-head 12 in connection. with av modified embodiment of my invention. In this case I draw the shield 3 against the end of the piston 1 by a long central rod 6 which passes through the entire length of the piston and is acted upon by a spring 7 placed at the outerend of the piston. This arrangement keeps the spring well away from the heat.

In this case the non-conducting material 5" is heldinside of a recess turned on the end of'the piston.

. In these embodiments of my invention I use helical springs for drawing the cap or shield against the piston and I prefer such springs for thepurpose. But it must be understood that other forms of springs may be used, such as fiat metal springs, or the proper arrangement of elasticmaterial such as india rubber, which would form an equivalent construction. It may be said that all materials are elastic and that a long rod in tension would form a spring, but such a construction would probably not afford sulficient elasticity. My invention is intended to cover any equivalent construction whereby the elasticity of any material. is intentionally utilized to aiford an. elastic pull holding a cap or shield against the end of a piston. 7

Although the construction covered by this invention is of particular value when a soft insulating material is interposed between piston and cap or shield, such insulating material may be omitted permitting direct contact between piston and cap, and the heat flow retarded by reducing as much as possible the extent of such direct contact.

What I cla'im is: Y 1. In an'internal' combustion engine, the

combination of a cylinder, a piston capable of reciprocation in said cylinder, a protective cap substantially covering the end of the piston which would otherwise be exposed to the working gases said cap being held against the end of the piston by spring pressure.

2. The combination of a piston for ini A ternal combustion engines, a cap or shield,

for the Working end of the piston, a layer or thickness of non-conducting material interposed between the said cap or shield and the.

tective cap or shield substantially covering the endof the piston against which the working gases act, and a helical metal spring orsprings holding said cap against the end of the piston. p

4. In an internal combustion engine, the combination of a cylinder, a piston capable of reciprocationdn said cylinder, a protectivecap or shield substantially covering the inner end of the piston against which the working gases act, and one or more helical metal springs disposed within said piston and arranged to draw said cap or shield against the said inner end of the piston. I

5. In an internal combustion engine, the combination'of a cylinder, a piston capable of reciprocation Within said cylinder, the

inner end of said piston being constructed to receive the pressure of the Working gases within the cylinder, a protective cap or shield substantially covering said inner end of the piston, a rod or rods secured at one end to'said cap or shield and extending into said piston, and a spring or springs engaging the inner end of said rods to hold the cap against the piston.

6. The combination of a piston for internal combustion engines, a cap or shield for the working end of the piston, a layer or layers of nonconducting material interposed between the said piston and the said cap or shield, a rod or rods engaging with the said cap or shield and passing through the end of the saidp'iston, and a spring or springs engaging with the said rod or rods.

7. The combination of a piston for internal combustion engines, a capor shield for the working end of the piston, a .central rod engaging wlth the said cap or'shield and passing through the endof the said piston and a spring or springs engaging with the said central rod and arranged to draw the said piston and the said shield to gether.

In witness whereof, I hereunto subscribe my name this 29th day of SepteInber A. D.,

GEORGE KLIADAVOL.

Witnesses R. B. TREAT, L. A. SMITH. 

